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This article belongs to the Special Issue Recent Advances in Metallic Nanoparticles as Theranostics Platforms., The development of nanoplatforms prepared to perform both multimodal imaging and combined therapies in a single entity is a fast-growing field. These systems are able to improve diagnostic accuracy and therapy success. Multicomponent Nanoparticles (MCNPs), composed of iron oxide and gold, offer new opportunities for Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) diagnosis, as well as combined therapies based on Magnetic Hyperthermia (MH) and Photothermal Therapy (PT). In this work, we describe a new seed-assisted method for the synthesis of Au@Fe Nanoparticles (NPs) with a flower-like structure. For biomedical purposes, Au@Fe NPs were functionalized with a PEGylated ligand, leading to high colloidal stability. Moreover, the as-obtained Au@Fe-PEG NPs exhibited excellent features as both MRI and CT Contrast Agents (CAs), with high r2 relaxivity (60.5 mM−1⋅s−1) and X-ray attenuation properties (8.8 HU mM−1⋅HU). In addition, these nanoflowers presented considerable energy-to-heat conversion under both Alternating Magnetic Fields (AMFs) (∆T ≈ 2.5 °C) and Near-Infrared (NIR) light (∆T ≈ 17 °C). Finally, Au@Fe-PEG NPs exhibited very low cytotoxicity, confirming their potential for theranostics applications, Financial support was provided the Ministerio de Economía, Industria y Competitividad (CTQ2017-86655-R), Ministerio de Ciencia e Innovación (PID2020-118448RB-C21, PID2020-113108RB-I00 (funded by MCIN/AEI/10.13039/50110001103), and PGC2018-096016-B-I00, the Fondo Social de la DGA (grupos DGA)), and by the Regional Ministry of Health of Andalusia (OH-0026-2018 and PAIDI 2020. P20_00727).

The total oxidation of methanol and toluene, chosen as representative VOCs, was investigated over CeO2- supported Au/FeOx catalysts prepared utilizing the bimetallic carbonyl cluster salt [NEt4][AuFe4(CO)16]. Characterization data showed that the catalysts prepared by the reported method exhibit highly and homogeneously dispersed iron oxide species on the ceria support together with small gold nanoparticles, whose size increases on increasing the amount of gold/iron. Addition of iron oxide species did not substantially increase the methanol combustion activity of ceria, whereas the presence of the mixed gold and FeOx species has been found to strongly enhance the activity towards the total oxidation of methanol. In the case of the toluene combustion the addition of FeOx or FeOx/Au species caused a significant decrease in the activity of the bare CeO2. The above catalytic behavior was rationalized on the basis of different interactions occurring among gold, iron oxide and cerium oxide, which synergically affects both the reactivity of the surface oxygen and the capacity of the support to adsorb the organic reactant.